lymphoid system : the lymphoid
tissue of the body considered collectively
lymphoreticular system : the tissues of the lymphoid and reticuloendothelial
systems considered together as one system
lymphatic system / systema lymphoideum / systema lymphaticum : the
lymphatic vessels and the lymphoid tissue, considered collectively
It can be divided into :
primary or central
lymphoid tissues, where lymphocytes differentiate from stem cells
hematopoietic bone marrow
of flat bones
=> vertebrae, sternum, ribs, iliac wings (in Aves it corresponds
tothe bursa of Fabricius)
from foetal week 20. It represents 4-6% of body weight and contains many
cell types, including stroma, bone marrow microvascular
endothelial cells (BMEC), adipocytes, osteoblasts and osteoclasts,
as well as mesenchymal
stem cells (MSCs)
The fatty degeneration of red bone marrow (RBM) (25%) into yellow
bone marrow (YBM) (75%) is completed around age 21 years.
early : E11.25 : the thymus domain of third pouch (high level of expression);
hair follicles and the epidermis frome E14.5
late : all TECs
thymic primordium forms but arrests between E11.5 and E12.5; no colonization
of primordium by lymphocytesref1,
Cell types :
thymic epithelial cells
/ LFA-3+MHC I+MHC
derive from epithelial tissues that originate from the 3rd pharyngeal
pouches and clefts complex during 6th week of pregnancy, while
T-lymphocytes (thymocytes) (there are no B cells !) derive
from bone marrow between week 7 and 14 of pregnancy. At the end of pregnancy
month 3 each lobe is made up of a central cordon (medullary substance)
surrounded by cortical substance : lobes are surrounded by a connectival
capsule and capsular septa divides each lobe into lobules
outer cortical cells are named nurse cells and each may engulf up
to 50 thymocytes
cortical TECs (cTECs) are predominantly K5-K8+K14-K18+
and rarely K5+K8+K14-K18+MTS20+
: a MTS24+ subpopulation of cTECs in the latter population are
concentrated at the corticomedullary junction (CMJ) and scattered
throughout the cortical and subcapsular regions, acting as precursors that
generate the former population
medullary TECs (mTECs) contains a major K5+K8-K14+K18-TR5+
subset and a minor K5-K8+K14-K18+
population that is distinguished from the cortical subset by globular morphology
europaeus agglutinin lectin binding properties.
some mTECs undergo calcification and necrosis and form the inner part of Hassall's
bodies or corpuscles / concentric corpuscles / Leber's corpuscles / thymus
corpuscles (spherical or ovoid bodies found in the medulla of the thymus,
composed of concentric arrays of epithelial cells which contain keratohyalin
and bundles of cytoplasmic filaments)
cTECs and mTECs share a common origin in bipotent precursors, providing
definitive evidence that they have a single rather than dual germ layer
origin during embryogenesisref.
This progenitor still persists after birth. To probe the function of postnatal
progenitors, a conditional mutant allele of Foxn1 was reverted to wild-type
function in single epithelial cells in vivo. This led to the formation
of small thymic lobules containing both cortical and medullary areas that
supported normal thymopoiesisref.
Hammar's myoid cells : striated muscle cells found in the thymus
of nonmammalian vertebrates, especially reptiles and birds, and rarely
Thymic crosstalk between epithelial cells and thymocytes occurs both
in the cortex and in the medulla thanks to thymic
thymulin / serum thymic factor / facteur thymique serique (FTS)
is a nonapeptide that needs a Zn2+ to express its immunoregulatory
also induces the synthesis of metallothioneins by TECs, which are thought
to be involved in the transfer of Zn2+ to thymulin and so in
the secretion of Zn2+-thymulin (also PRL and IGF are stimulating
factors). The administration of an Lys-Arg to elderly individuals and cancer
patients can increase the synthesis and/or release of thymulin to normal
levels and also increases the number of peripheral T-cell subsets.
thymic humoral factor (THF) is a polypeptide of 3.2 kDa. It promotes
production in intact and thymus-deprived mice and augments lymphocyte proliferation
vitro and in vivo. The octapeptide THF-g2
has the amino acid sequence Leu-Glu-Asp-Gly-Pro-Lys-Phe-Leu : it plays
a stimulatory role on human myeloid and erythroid hematopoietic progenitor
cells, reconstituting the defective CMI in patients with various types
of neoplasms and secondary immune deficiencies as a result of chemo and/or
has been shown to hydrolyze THF-g2
with high efficiency.
thymocyte growth peptide (TGP) is a formylpteroyl-Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn.
Native TGP contains Zn2+, which counteracts degradation of the
molecule and is required for full biological activity.
(Tpo) is a protein of 49 amino acids. 3 variants having largely
identical sequences have been described (e.g. thymopoietin-3 (TP-3)
/ splenin has been isolated from bovine spleen).
Thymopoietin specifically interacts with the neuronal N receptors and can
regulate the a-bungarotoxin binding sites. Thymopoietin
induces the phenotypic differentiation of T precursor cells in vitro
while inhibiting phenotypic differentiation of B-cells.
thymopoietin 32-36 or thymopentin
(TP-5) is Arg-Lys-Asp-Val-Tyr, corresponding to amino acids 32-36 of
thymopoietin. It appears to represent the active site of thymopoietin in
that it has all the biological activities of the native hormone. Some analogs
of TP-5, for example TP-3 (Arg-Lys-Asp), and TP-4 (Arg-Lys-Asp-Val)
exhibit significant immuno stimulating potencies in vitro and in
vivo exceeding those of thymopentin. Thymopentin is able to increase
IL-2 and IL-2R production. TP-5 enhances bone marrow NK cells, probably
by permitting the maturation of their precursors, and also NK activities
in PBMCs of patients having received the drug 3 times per week for 1 month
(50 mg sc). TP-5 has been found also to be useful in the treatment of a
subgroup of patients with Sezary
Thymopentin also induces ACTH-like immunoreactivity release by human lymphocytes.
is expressed in human kidney, liver, spleen, normal
lymphocytes (predominantly T-cells), HTLV-infected T-cells, and myeloma
cells. It enhances allo- and auto-Ag-induced human T-cell proliferation
and MHC II
antigen expression in APCs. It has been shown to potentiate or fully restore
the deficient cytotoxic effector function of peripheral mononuclear cells
in patients with advanced malignancies. Thymosin-a1
is a protein of 28 amino acids (3.1 kDa) which is derived from the NTDs
of prothymosin-a. A variant lacking 4 carboxyterminal
amino acids [des-(25-28)-thymosin-a1]
and another variant possessing 7 additional carboxyterminal amino acids
[thymosin-a11] have been isolated
from calf thymus fractions. Thymosin-a11,
in doses of < 300 ng per mouse, protects susceptible inbred murine strains
against opportunistic infections with Candida
and shows approximately the same potency as thymosin-a1.
Thymosin-a1 can induce in vitro
differentiation of human thymocytes to Th1
cells. It also induces terminal differentiation of functionally immature
cord blood lymphocytes and has been shown to induce the production of IL-2,
high affinity IL-2Rs, and BCGFs by PBMCs. Th and Tc
populations are targets of thymosin activity. In nude mice thymosin-a1
appears to exert its effect at an early stage of T-cell differentiation
and induces a T-cell subpopulation capable of producing IL-3
(but not yet IL-2).
Thymosin-a1 and thymosin-b4
have been shown to increase the efficiency of Ag presentation by macrophages.
Thymosin-a1 has been found also to
be an endogenous modulator of a-thrombin activity.
Thymosin-a1 has been suggested to
play a role as an autocrine growth modulator for the human breast cancer
cell line MCF-7 in culture. Thymosin-a1
has been shown to down-regulate the growth of human non-small
cell lung cancer (NSCLC)
cells in vitro and in vivo.
a peptide isolated from rat thymus, contains approximately 101 amino acids.
It shows 43% structural identity with thymosin-a1
and prothymosin-a in the first 30 aminoterminal
amino acids. Parathymosin-a appears to modulate
the action of prothymosin-a in protecting sensitive
strains of mice against opportunistic infection with Candida
and has been shown to block the in vivo immunoenhancing effects
(paralog genes on X
chromosome (escapes X inactivation and encodes an actin sequestering protein)
chromosome) is a protein of 43 amino acids with an acetyl-Ser aminoterminus
isolated originally from calf thymus. It is produced also by some cell
lines, including myoblasts and fibroblasts and also appears to be produced
by some human medullary thyroid carcinomas. Thymosin-b4
has been shown to be induced during differentiation of bone marrow cells
induced by GM-CSF.
Human thymosin-b4 has been found
to be identical with the human interferon-inducible gene 6-26 and
a protein involved in actin polymerization : it sequesters G-actin monomers
and inhibits actin polymerization. Thymosin-b4
induces the expression of TdT
in thymocytes in vivo and in vitro and thus appears to act
on lymphoid stem cells, probably controlling the early stages of the maturation
process of thymus-dependent lymphocytes. Thymosin-b4
has been found also to be an activator of CaM-dependent enzymes in the
hypothalamus. It also improves and normalizes suppressor cell activities
in diabetic patients. Thymosin-b4
can undergo enzymatic cleavage in vitro and in vivo and yields
a tetrapeptide that functions as a negative regulator of hematopoiesis
. Thymosin-b4 by itself has been
shown to act as an inhibitor for normal human CD34+ hematopoietic
progenitor cells, decreasing the growth of both granulo-macrophagic and
erythroid progenitors. A fusion protein constructed from TNF with human
thymosin-b4 has been shown to have
significant antitumor effects in experimental tumor-bearing animals after
systemic injection : the fusion protein had a significantly higher t1/2
in serum than the original TNF and caused regressions of tumors at concentrations
at which TNF was inactive.
thymosin-b8 contains 39 amino
acid residues, of which 31 are identical with the corresponding amino acid
residues in thymosin-b4. The NH2
terminus of thymosin-b8 is acetyl-Ala,
compared with acetyl-Ser in thymosin-b4.
thymosin-b9 (41 amino acids)
is identical with thymosin-b8 except
for the presence of an additional dipeptide, -Ala-Lys-OH, at the carboxy
terminus. 32 of its 41 amino acids are identical with those of thymosin-b4.
is composed of 43 amino acid residues and shows 75% sequence homology with
thymosin-b4. A comparison of human
and rat thymosin-b10 cDNA sequences
reveal 100% identity for the deduced amino acid sequence and 95% nucleotide
identity for the coding region. Thymosin-b10
has been found to be expressed abundantly in embryonic/fetal human brain
but absent in adult tissues and probably plays an important role in early
neuroembryogenesis and neural maturation. Thymosin-b10
mRNA appears to be expressed specifically in highly metastatic human melanoma
cells lines and may be progression marker for human cutaneous melanoma.
Thymosin-b10 has been shown also
to function as an actin monomer sequestering protein (see: Fx).
thymosin-b11 isolated from
rainbow trout (Oncorhynchus
mykiss (a.k.a. Salmo gairdneri)) spleen
contains 41 amino acids and is 78% homologous to thymosin-b4.
Thymosin therapy has been reported to promote disease remission and cessation
of HBV replication in patients with chronic viral infection. The protein
shows a high degree of sequence homology with thymosin-b12.
thymosin-b12 has been isolated
from perch liver and rainbow trout (Oncorhynchus
mykiss (a.k.a. Salmo gairdneri)) spleen.
The protein is 43 amino acids in length and sequence analysis reveals that
it is 79% homologous to thymosin-b4
and that it shows 84% sequence homology with thymosin-b11.
thymosin-b15 has been found
to be upregulated in the highly motile and metastatic Dunning rat prostatic
carcinoma cell lines. Experiments with antisense thymosin-b15
RNA demonstrate that thymosin-b15
positively regulates cell motility, which has been demonstrated to correlate
with the metastatic phenotype. Levels of thymosin-b15
levels are elevated also in human prostate
cells and correlate positively with the Gleason tumor grade.
... and cytokines (IL-1b),
is produced by cortical stromal cells and induces thymocyte migration via
cTECs create the hematothymic barrier
(a.k.a. blood-thymus barrier), which breaks only near the corticomedullary
junction (CMJ), where T-lymphocytes enter bloodstream.
The thymus exports 2% of total thymocytes each day : this number decresaes
of 3% per year during the first 3 decades of life.
The thymus has the greatest relative size in newborn and the greatest
absolute size at puberty : after puberty the thymic parenchyma undergoes
(cortical thymocytes are replaced by adipous tissue), leading to a slow
decline in immune function up to 50, where no function is detectable. It
also involutes during pregnancy for reasons that are not yet clear.
2 cytokines of the IL-6 family, LIF
can cause thymic atrophy with loss of cortical thymocytes : the latter
can transform the lymph node into a primary lymphoid organ whose ability
to support T cell development and to seed peripheral compartments is similar
to that of a normal thymus ! Thymocyte selection is active during fetal
and neonatal period, but the levels of glucocorticoids
circulating in the fetus are low because some level of protection from
maternal glucocorticoids is provided by the placenta that contains high
levels of the GC-catabolizing enzyme 11b-HSD
The necessity of them for positive selection of thymocytes has led to the
hypothesis that there may be local production of glucocorticoids in the
thymus during development : cultured TECs do produce pregnenolone and deoxycorticosterone,
and this production can be increased by ACTH.
Thymic posttranslational GR knock-outs by RNAi indicate necessity of glucocorticoids
in thymocyte development and differentiation, but in time-controlled systemic
knock-outs no difference in CD4+CD8+ thymocytes is
found. GR knockout mice have been described that die at E19 : however up
to E18 these animals have apparently normal thymocyte populations and T
cell development, suggesting that GR in this case is not necessary for
the entire process of T cell development and differentiation. The thymus
is richly innervated : acute stress results in a rapid loss of cortical
thymocytes thought to be at least partly due to the effect of glucocorticoids
and endogenous opioids.
secondary or peripheral
lymphoid tissues or organs (SLO), where lymphocytes take part in immune
It is widely accepted that the trafficking of intravascular leukocytes
is controlled by a sequence of at least 3 molecularly distinct adhesion
and signalling eventref1,
These adhesion cascades are initiated by a tethering step that allows leukocytes
to bind loosely to endothelial cells (step 1a). The marginated cells are
then pushed forwards by the blood stream resulting in slow rolling along
the vessel (step 1b). Subsequently, rolling cells encounter chemotactic
stimuli on the endothelium that engage specific leukocyte receptors (step
2). Chemoattractant binding, in turn, induces intracellular signals triggering
activation-dependent adhesion steps that allow leukocytes to stick firmly
(step 3) and to emigrate through the vessel wall (step 4). Intravital microscopy
analyses have defined the adhesion cascades that mediate T- and B-cell
homing to LNsref1,
Early electron-microscopy studies indicated that homing lymphocytes migrate
into and across individual high endothelial cells before entering either
the basolateral interendothelial junction or the subendothelial spaceref.
However, others observed that diapedesis occurs through interendothelial
There is also uncertainty about the adhesion-molecule requirements for
lymphocyte migration through endothelial monolayers without a chemotactic
However, in intravital microscopy experiments, T cells rarely emigrate
into surgically exposed LNs even though they roll and arrest at a high
frequency, and numerous T cells emigrate into undisturbed LNs of the same
This indicates that a crucial fctor is lost during surgical tissue preparation
that is required for lymphocytes to undergo diapedesis. As blood flow is
always intact, fluid shear flow is probably not sufficient for lymphocyte
diapedesis in HEVs. Another interesting issue is whether, and to what extent,
transendothelial migration occurs in an abluminal-to-luminal directionref
: reverse migration across HEVs is probably not unique for pigs, even though
its frequency varies between species. The phenotype and immunological function
of cells migrating in reverse and the traffic signals that control this
unorthodox behaviour are unknown.
In each organs the boundary between T-cell zones (TCZ) and B-cell
zones (BCZ) is defined by the following chemokine --- receptor interactions
--- CD195 / CXCR5
(limits B-cell migration up to the T/B boundary but not into T-cell zone)
lymphatic capillaries (unconstant
Ø, up to 30÷60 mm) : present in
those organs which have connective tissue. Absent in CNS, PNS, placenta,
umbilical cord, cornea and cartilage. In liver, kidney, lungs, heart, pancreas
and many endocrine glands the lymphatic network is much smaller than the
blood vessels network. They form plexus around arteries. No basal lamina,
pores, fenestrae, pericytes. Open junctions between endothelial cells.
lymphatic plexus : an interconnecting
network of lymph vessels, i.e., the lymphocapillary vessels, collecting
vessels, and trunks, which provides drainage of lymph in a one-way flow.
plexus jugularis / jugular plexus : a plexus of lymphatic vessels
along the internal jugular vein
plexus lymphaticus axillaris / axillary lymphatic plexus : a plexus
of lymph vessels and nodes in the fossa axillaris.
Sappey's subareolar plexus : a lymphatic plexus situated beneath
the areola of the nipple.
plexus aorticus : a network of lymphatic vessels about the aorta.
plexus coeliacus / celiac plexus /
plexus celiacus : a plexus composed of lymphatic vessels, the superior
mesenteric lymph nodes, and the celiac lymph nodes behind the stomach,
duodenum, and pancreas.
plexus hypogastricus : a plexus of lymphatic vessels in the hypogastric
plexus iliacus externus : a lymphatic plexus situated about the
external iliac vessels.
plexus inguinalis / inguinal plexus : a lymphatic plexus situated
near the end of the long saphenous vein and along the femoral artery and
vein in the iliopectineal fossa
plexus sacralis medius : fine network of lymphatic vessels in the
hollow of the sacrum.
plexus lumbalis / lumbar plexus : a lymphatic plexus in the lumbar
Panizza's plexuses : 2 plexuses of the lymph vessels in the lateral
fossae of the frenum of the prepuce.
Quénu's hemorrhoidal plexus : a lymphatic plexus found in
the perianal skin.
precollectors : thick basal lamina and rarely smooth muscle cells.
Uneffective valves. Along their way are located interrupting lymph nodes,
with variable distribution.
lymphatic collectors : along
their way are regularly located lymph node stations (more than one
large lymph node), sometimes grouped into lymph centres. Many effective
semilunar valvula lymphaticum / lymphatic valve (any of the usually
doubled cusps in the collecting lymphatic vessels, serving to ensure flow
in only one direction). 2 antiparallel helicoidal layers of smooth muscle
cells (except that near valves). No elastic tissue, anchoring to tissue.
superficial (above fascia comune, in subcutaneous tissue, independently
by blood vessels). Effector and sensitive innervations.
deep (below common fascia, satellite to blood vessels)
According to their location regarding to lymph node, they are named :
afferent or prelymph-nodal collectors
efferent or postlymph-nodal collectors
trunci lymphatici / lymphatic trunks
: the lymphatic vessels (right or left lumbar, intestinal, right or left
bronchomediastinal, right or left subclavian, and right or left jugular
trunks) that drain lymph from various regions of the body into the right
lymphatic or thoracic duct.
trunci intestinales / intestinal
trunks : short lymphatic vessels which leave the gastrointestinal tract
and participate in formation of the thoracic duct
truncus jugularis / jugular trunk
: either of the 2 vessels, right and left, draining the deep cervical lymph
nodes: on the right side, into the right lymphatic duct or subclavian vein,
and on the left side, into the thoracic duct or subclavian vein.
truncus subclavius / subclavian
trunk : either of 2 lymphatic vessels, right and left, draining the
axillary lymph nodes; that on the right into the right lymphatic duct or
subclavian vein, that on the left into the thoracic duct or the subclavian
truncus bronchomediastinalis / bronchomediastinal
trunk : either of the 2 lymphatic vessels, right and left, draining
the pulmonary, bronchopulmonary, tracheobronchial, tracheal, and parasternal
lymph nodes: that on the right side into the right lymphatic duct or subclavian
vein, and that on the left into the thoracic duct or the subclavian vein.
truncus lumbalis or lumbaris / lumbar
trunk : either of the 2 lymphatic vessels, right and left, draining
lymph upward from the lumbar lymph nodes and helping form the thoracic
principal lymphatic ducts / ductus
lymphatici : the main lymph channels into which the converging lymph
vessels drain, which in turn empty into the blood stream. Effective valves.
Effector and sensitive innervations.
ductus lymphaticus dexter / right
lymphatic duct : a vessel draining the lymph from the upper right side
of the body, typically formed by the right jugular, subclavian, and bronchomediastinal
lymphatic trunks, any one of which may, however, end separately in the
right brachiocephalic vein; when all 3 lymphatic vessels unite, a right
lymphatic duct (called also ductus thoracicus dexter / right thoracic
duct) is formed, which empties directly into the junction of the internal
jugular and subclavian veins.
ductus thoracicus / thoracic duct
: the largest lymph channel in the body, which collects lymph from the
portions of the body below the diaphragm and from the left side of the
body above the diaphragm; it begins in the abdomen (pars abdominalis)
at the junction of the intestinal, lumbar, and descending intercostal trunks
(which consists of a plexus or the cistern
of Pecquet / cisterna chyli / ampulla chyli / chylocyst / Pecquet / receptaculum
chyli / receptaculum Pecqueti : a dilated portion of the thoracic duct
at its origin in the lumbar region; it receives several lymph-collecting
vessels, including the intestinal, lumbar, and descending intercostal trunks)
at about the level of L2 vertebra, enters the thorax through the aortic
hiatus of the diaphragm (pars thoracica), ascends to cross the posterior
mediastinum, and enters the neck (pars cervicalis), where it forms
a downward arch (arcus ductus thoracici) across the subclavian artery,
and ends at the junction of the left subclavian and internal jugular veins.
lymph nodes (LN) / nodus lymphaticus
/ lymphoglandula / lymphonodus / nodus lymphoideus function as an immunologic
filter for lymph, varying from 1 to 25 mm in diameter (see also diseases
of lymph nodes)
(reproduced with permission from Nature
Reviews Immunology (Vol 3, No. 11, pp 867-878 (2003)) copyright
Macmillan Magazines Ltd)
trabeculae nodi lymphatici or lymphoidei / trabeculae of lymph node
: strands of dense connective tissue radiating out from the capsule through
the interior of the node
cortex: many architectural elements
(cords, channels, corridors and the fibroblastic reticular cell (FRC) conduits)
facilitate cell interactions. The fine structure of the LN cortex is complex
but nevertheless, common structural features have been identifiedref1,
T cell zone (paracortex : T/B ratio
3:1) : on the base of electron-microscopy strudies, it has been proposed
that the paracortex is arranged in paracortical cords that originate
between or below the B-cell follicles and extend towards the medulla where
they merge into medullary cordsref.
It is the site where circulating lymphocytes enter the LNsref
and where T-cell interact with DCsref.
The cords are bordered by lymph-filled cortical sinuses and permeated by
reticular fibres. At the centre of each paracortical cord is an HEV that
is surrounded by concentric layers of pericytes known as fibroblastic
reticular cells (FRCs). A narrow space between the basement of the
HEV and the pericytes is known as the perivenular channel. It has
been propose that this channel receives an ultrafiltrate of lymph from
the FRC conduit. Networks of FRCs that are often arranged in spiral layers
around the HEVs enclose 10-15 mm wide corridors
along which lymphoytes are thought to migrateref1.
B-cell zone (more superficial) that consists of ...
primary follicles : they contain
B cells and FDCs.
Under unknown stimuli, Ag-specific B-cells migrate to the paracortex, where
they are activated by Th cells (the latter are activated by
Once activated, both Th cells and B-cells migrate back to the
primary lymphatic follicle, where FDCs
germinal centre (GC) / Flemming centre
/ secondary nodule : the area in the center of a lymph nodule containing
aggregations of actively proliferating Ag-activated B-cell blasts that
have migrated into the follicle lymph nodes; it appears as a spherical
mass surrounded by a capsule of elongated cells that is partially invested
by a crescentic cap of small lymphocytes.
B cell clones which express mIg molecules with high affinity for the Ag
presented by FDCs
are selected for (positive selection) and continue to proliferate.
B cell clones which fail to recognize antigen or express low affinity mIg
molecules die by apoptosis and are phagocytosed. This accounts for affinity
maturation, also via somatic
differentiation into memory or plasma cells before leaving the GC. Also
rare Th cells are present.
segregation of B cells to the dark and light zones of GCs,
in which they carry out SHM and antigen-driven selection, respectively,
depends on chemokines :
centroblasts undergoing SHM express high levels of CXCR4
and localize to the dark zone, which is consistent with higher expression
of its ligand CXCL12
in the dark zone compared with the light zone
by contrast, expression of CXCR5
and its ligand CXCL13 / BLC
are concentrated in the light zone and contribute to recruitment of centrocytes
to this zoneref.
3-4 antigen-specific B cells colonize a follicle to establish a GC and
become rapidly dividing GC centroblasts that give rise to dark zones. Centroblasts
produce non-proliferating centrocytes that are thought to migrate to the
light zone of the GC, which is rich in antigen-trapping FDCs and CD4+
T cells. It has been proposed that centrocytes are selected in the light
zone on the basis of their ability to bind cognate antigen. However, there
have been no studies of GC dynamics or the migratory behaviour of GC cells
in vivo. The direct visualization of B cells in lymph node germinal
centres by 2-photon laser-scanning microscopy in mice. Nearly all antigen-specific
B cells participating in a GC reaction were motile and physically restricted
to the GC but migrated bi-directionally between dark and light zones. Notably,
follicular B cells were frequent visitors to the GC compartment, suggesting
that all B cells scan antigen trapped in GCs. Consistent with this observation,
high-affinity antigen-specific B cells can be recruited to an ongoing GC
reaction. The open structure of GC enhances competition and ensures that
rare high-affinity B cells can participate in antibody responsesref.
follicular mantle zone (naive
mature CD5+ IgM+IgD+ B cells displaced
by an expanding germinal centre). They are often mixed with marginal zone
B-cells (CD5-IgM+IgD-) equivalent to those
of spleen marginal zone
medulla(mainly a B-cell zone) is a
labyrinth of lymph draining sinuses that are separated by medullary cords,
which contain many plasma cells, and some macrophages and memory T cells.
The function of the medulla is still poorly understood : activated B cells
committed to becoming plasma cells migrate to the medulla where they develop
into Ab-producing plasma cells. Some memory B cells remain in the lymph
node while others leave by efferent lymphatic vessel and reach target organ(s).
the only efferent lymphatic vessel that exit from the ...
hilus : a discrete region where the capsule is penetrated by efferent
lymph and blood vessels
the microvascular anatomy and haemodynamics have been characterized in
mouse inguinal LNsref
blind-ending afferent lymph
collect and channel interstitial fluid, enter capsular
septa and open into the marginal
or subcapsular sinus (a bowl-shaped lymph sinuses separating the capsule
that covers the LN from the cortical parenchyma of a lymph node), from
which lymph flows into the cortical
or intermediate sinuses (lymph sinuses in the cortex of a lymph node,
which arise from the marginal sinuses). From here, the lymph is drained
towards the hilus through the fibroblastic
reticular cell (FRC) conduit and, through trabecular
sinuses, across the LN parenchyma towards medullary
sinuses (lymph sinuses in the medulla of a lymph node, which divide
the lymphoid tissue into a number of medullary cords). The intranodal lymph
channels are enclosed by fibroblastic
reticular cells (FRCs)ref,
receptor-expressing sinus-lining endothelial cellsref1,
and, expecially in the subcapsular sinus, macrophages and CD11b+
which sample the lymph and remove microorganisms and debris that are in
it. These cells also transport and/or process antigenic material for presentation
to B and T cells. The T-cell rich paracortical cord (light blue) is shown
adjacent to a B-cell follicle (pink) and demarcated by lymph-filled sinuses
(green). The paracortical cord is penetrated by reticular fibres consisting
of type 1 and type 3 collagen that are contained within the sleeves of
the FRCs forming a conduit. At the centre of each cord is a high
endothelial venule (HEV)
that is surrounded by concentric layers of FRCs. The FRC conduit drains
lymph into the perivascular channel. Afferent lymph is the main
route by which antigens reach LNs. 2 mechanisms of antigen delivery cnn
antigenic material becomes lymph borne and is taken up by DCs in a LN :
this requires that the LNs are continuously stocked with immature DCs that
can uptake and process antigens. CD11b+ (myeloid) DCs are concentrated
in the superficial paracortex, well positioned to capture lymph-borne proteins
from the subcapsular sinusref.
The progeny of Langerhans cells as well as CD8ahi
(lymphoid) DCs and plasmacytoid DCs are distributed throughout the T-cell
area in LNsref1,
The route(s) by which LNs are supplied with these resident subsets are
probably diverse. Langerhans cells give rise to CD8alow
or CD8a+ DCs in LNs, indicating this
population enters the LNs through the lymph. Plasmacytoid DCs express L-selectin,
and it has been porposed that they migrate to LNs through HEVsref1,
Antibody specific for L-selectin blocks the marked increased of both CD8a+
and CD8a- DCs in LNs of virus-infected
mice, but conclusive proof for L-selectin-dependent DC homing through HEVs
awaits careful homing experiments.
antigen is acquired by DCs in peripheral tissues and the DCs can then carry
the processed antigen to draining LNsref
Free antigen and/or antigen-loaded DCs are
transported to the LNs from distal tissues through afferent lymph vessels.
Lymph-borne molecules do not have free acces to the lymphocyte compartment.
Only small molecules with a molecular radius < 4 nm can reach the T-cell
area through the FRC conduit. FRCs wrap around collagen fibres, forming
channels that project from the subcapsular sinus into the T-clell area.
So, the FRC imposed size barrier to lymph-borne molecules might not be
absolute, but select macromolecules, such as antibodies, can gainaccess
to the nodal parenchyma by mechanisms that remain to be identified. LNs
must also function as sites of innate recognition of lymph-borne pathogens
: microorganisms that breach the body's surface barriers can use the lymphatics
to reach the systemic circulation and to disseminate : good examples are
(LNs infected by less virulent Yersinia strains recruit numerous
inflammatory cells. So, it has been speculated that the success of Y.pestis
be due to its ability to block the recruitment of phagocytes to the LNs),
... Initial evidence that the FRC conduit can influence leukocyte recruitment
came from experiments in plt/plt
in which defective T-cell homing was restored by intracutaneous injection
but not CXCL12ref1,
The exogenously applied chemokines were rapidly transported to HEVs and
presented to rolling T cells in the lumen of the vessel. Chemokine transcytosis
in abluminal-to-luminal direction was first described in dermal venules
where it involved the caveoli networkref.
Similarly, chemokines transverse HEVs in intracellular vesicles rather
than across intercellular junctionsref,
but these transport vesicles are still incompletely characterized. So far,
the list of chemokines that were shown to be transported from a non-endothelial
source to LN HEVs include :
from inflamed skinref
gets released into the lymph, transported to draining LNs, and translocated
to the luminal surface of HEVs where it activates CCR2 on rolling monocytes,
triggering integrin-mediated arrestref
interaction with CXCR3
has been defined as a second mechanism for monocyte recruitment to LNs
that drain inflamed tissuesref,
but it is not known whether CXCL9 is produced by the inflamed HEVs or by
other intra- (or extra-) nodal cells from where the chemokine might have
The ability to modulate multi-step adhesion cascades in HEVs remotely by
secreting chemokines into the lymph enables peripheral tissues to control
the composition and function of leukocytes in draining LNs. It is conceivable
that this mechanism opens a gate to LNs not only for monocytes, which might
then give rise to macrophages and/or DCs, but also for other circulating
leukocytes, such as granulocytes, which express L-selectin and LFA1 and
several receptors for inflammatory chemokinesref. However, recent work
indicates that there are are also counter-regulatory mechanisms :
venous blood flows through high
endothelial venule (HEV)
along a venular tree, the trunk of which is formed by a large collecting
venule in the medulla. This venule drains into a large vein at the hilus.
Adhesive interactions between leukoctes and endothelial cells are absent
in LN arterioles and capilaries, but they occur frequently in venules :
recent work indicates that the medulla-associated segments of the venular
tree express unique adhesion molecules that are distinct from those expressed
Some T and B memory lymphocytes reach LNs
from peripheral tissues through the afferent lymph vesselsref,
but all T and B naive lymphocytes enter
these organs in high endothelial venules (HEVs)ref1,
This route of lymphocyte traffic is highly efficientref1,
A single inguinal mouse LN recruits 2% of the recirculating pool per dayref.
During inflammation, lymphocyte accumulation in draining LNs is markedly
whereas their exit into the efferent lymphatics is transiently blockedref,
rapidly increasing lymphocyte numbers in the draining LNs, which might
enhance the probability for antigen encounter by the rare T cells that
express a relevant TcR. Lymphocyte homing remains inconsequential unless
lymphocytes are presented with antigen by DCsref
: if they fail to recognize specific antigen within a few hours, they return
to the circulation through efferent lymph vessels and the thoracic ductref.
Homed lymphocytes in pig LNs leave through HEVs rather than through efferent
Electron-microscopy studies of rat LNs found that 92% of lymphocytes in
HEVs migrated towards the nodal parenchyma, whereas the remainder were
oriented towards the lumenref.
We have little knowledge about what determine show long lymphocytes stay
in the LNs. A few adhesion molecules have been identifed on intranodal
lymphatics. These include the pan-endothelial-cell marker CD31
/ PECAM1a - the mannose receptor, which interacts with p90-110L-selectin
/ CD62L / MEL-14 / LAM-1 / LECAM-1 / Leu-8ref
- and common lymphatic endothelial and vascular endothelial receptor
1 (CLEVER1), an adhesion molecule with as-yet-unknown ligand specificity
that is also expressed by HEVsref1,
Classic experiments in sheep have shown that transient antigen challenge
precipitates a transient (6-18 hours) reduction in lymphocyte egress into
efferent lymph vessels despite a several-fold increase in lymphocyte recruitment
The decrease in lymphocyte output is most marked with viral and bacterial
challenges and is lower or absent in response to noninfectious stimuli.
Over several days after challenge, cell output in efferent lymph rises
markedly, reaching a peak at day 3 to 4. Although the signals that regulate
the magnitude of lymphocyte entry and egress in LNs are still unknown,
a hint has come from studies of FTY720 : whatever the precise mechanism(s),
together these observations raise the possibility that S1P
and its receptors (particularly EDG1
and EDG6 / S1P4)
are involved in regulating the overall lymphocyte content in LNs.
an unresolved issue is that intraperitoneal injection of a protein antigen
can elicit T-cell responses in distant LNs that do not receive lymph from
the injection siteref.
How does such antigen enter LNs, how is it processed and presented?
nodi lymphoidei parietales / parietal lymph nodes : lymph nodes
that receive lymph from the walls of a body cavity
nodi lymphoidei viscerales / visceral lymph nodes : lymph nodes
that receive lymph from the viscera in a body cavity; cf. nodi lymphoidei
head and neck lymph nodes (a.k.a.
oral, and nasal-associated lymphoid tissue (CONALT))
nodi lymphoidei occipitales / occipital
lymph nodes : several small nodes near the occipital insertion of the
semispinalis capitis muscle.
superficial lymph nodes (1÷6)
deep lymph nodes (1÷3)
nodi lymphoidei mastoidei / mastoid lymph nodes / nodi lymphatici retroauriculares
lymph nodes / posterior auricolar lymph nodes (1÷4) : lymph
nodes, 2 or 3 on each side, that are superficial to the mastoid attachment
of the sternocleidomastoid muscle and deep to the posterior auricular muscle;
they drain the nasal fossae and paranasal sinuses, hard and soft palate,
middle ear, and nasopharynx and oropharynx.
nodi lymphoidei parotidei / parotid
nodi lymphoidei parotidei superficiales / superficial parotid lymph
nodes : lymph nodes lying in the subcutaneous tissue of the parotid
gland directly in front of the tragus.
anterior auricolar lymph nodes
inferior auricolar lymph nodes
nodi lymphoidei parotidei profundi / deep parotid lymph nodes :
lymph nodes on the lateral wall of the pharynx lying deep to or embedded
in the deep substance of the parotid gland, through which lymph drains
from the external acoustic meatus, auditory tube, tympanum, soft palate,
and posterior nasal cavity.
extraglandular lymph nodes
nodi lymphoidei parotidei profundi infraauriculares / infra-auricular
deep parotid lymph nodes : deep parotid lymph nodes situated below
nodi lymphoidei parotidei profundi intraglandulares / intraglandular
deep parotid lymph nodes : deep parotid lymph nodes situated within
the substance of the parotid gland. (4÷10)
nodi lymphoidei parotidei profundi preauriculares / preauricular deep
parotid lymph nodes : deep parotid lymph nodes situated in front of
nodi lymphoidei faciales / facial
lymph nodes : lymph nodes situated along the course of the facial artery
and vein, which receive afferent vessels draining the eyelids, conjunctiva,
nose, cheeks, lips, and gums, and send efferent vessels to the submandibular
nodus lymphoideus malaris / malar lymph node : one of a variable
number of facial lymph nodes situated in the region of the zygomatic minor
nodus lymphoideus mandibularis / mandibular lymph node : one of
a variable number of facial lymph nodes situated near the angle of the
mandible, into which lymph from some of the superficial tissues of the
head and neck is drained.
nodus lymphoideus buccinatorius / buccinator lymph node / buccal lymph
node and nodus lymphaticus buccalis : one of a variable number of facial
lymph nodes lying on a line between the angle of the mandible and the mouth,
receiving the afferent vessels draining the temporal and infratemporal
fossae and nasopharynx; their efferent vessels drain into the superior
deep cervical nodes
nodus lymphoideus nasolabialis / nasolabial lymph node : one of
a variable number of facial lymph nodes situated near the junction of the
superior labial and facial arteries, which drains the upper lip and external
nose into the submandibular node.
nodi lymphoidei submandibulares / submandibular
lymph nodes : the 3 to 6 nodes alongside the submandibular gland, through
which lymph drains from the adjacent skin and mucous membrane (deep : 5÷8)
nodi lymphoidei submentales / submental
lymph nodes : nodes under the chain into which the lymph from some
of the superficial tissues of the head and neck is drained (superficial
nodi lymphoidei retropharyngeales / retropharyngeal
lymph nodes : deep lateral cervical lymph nodes, one median and two
lateral groups, situated behind the upper part of the pharynx, especially
concerned with drainage of the nasal fossae, paranasal sinuses, hard and
soft palates, middle ear, nasopharynx, and oropharynx. (deep: 2÷4)
node of Rouvière : the most superior of the lateral group
of the retropharyngeal lymph nodes, located at the base of the skull
nodi lymphoidei linguales : deep cervical lymph nodes receiving
afferent vessels from the tongue.
nodi lymphoidei cervicales laterales profundi / deep
lateral cervical lymph nodes : a chain of lymph nodes situated in the
posterior cervical triangle; the chain is subdivided into smaller chains
of lymph nodes, including a
nodus lymphoideus jugulodigastricus / jugulodigastric lymph node / hauptganglion
of Küttner / Küttner's ganglion : one of the deep lateral
cervical lymph nodes lying on the internal jugular vein at the level of
the greater cornu of the hyoid bone, i.e., just below the posterior belly
of the digastric muscle
nodus lymphoideus juguloomohyoideus / jugulo-omohyoid lymph node
: one of the deep lateral cervical lymph nodes lying on the internal jugular
vein just above the tendon of the omohyoid muscle.
nodi lymphoidei cervicales laterales superficiales / superficial
lateral cervical lymph nodes (4÷5) : lymph nodes situated along
the external jugular vein that send efferent vessels to the deep lateral
cervical lymph nodes.
nodi lymphoidei cervicales laterales profundi inferiores / inferior deep
cervical lateral lymph nodes / substernocleidomastoideal deep cervical
lymph nodes (15÷30) : a group of lymph nodes adjacent to the
carotid sheath, partly deep to the sternocleidomastoid muscle and extending
into the subclavian triangle. They receive lymph from the back of the scalp
and neck, the tongue, the superficial pectoral region, and part of the
arm and drain into the jugular trunk.
nodi lymphatici jugulares laterales / lateral jugular lymph nodes
: deep lateral cervical lymph nodes situated lateral to the internal jugular
vein that empty into the jugular trunk.
nodi lymphoidei accessorii / accessory nodes : a chain of lymph
nodes of the inferior deep lateral cervical group that follow the spinal
accessory nerve and receive lymph from the occipital, postauricular, and
suprascapular nodes and from the scalp, neck, and shoulder.
nodi lymphoidei supraclaviculares / supraclavicular lymph nodes
: the deep lateral cervical lymph nodes situated inferior to the omohyoid
muscle, extending into the omoclavicular portion of the posterior triangle
of the neck.
nodi lymphoidei cervicales laterales profundi superiores / superior
deep cervical cervical lymph nodes / supraclavicular deep cervical lymph
nodes : a group of lymph nodes adjacent to the carotid sheath deep
to the sternocleidomastoid muscle; they receive lymph from a number of
structures of the head and neck and drain into the inferior deep cervical
nodes or the jugular trunk.
nodi lymphoidei cervicales anteriores / anterior
cervical lymph nodes : a group of lymph nodes ventral to the larynx
and trachea, consisting of superficial vessels on the anterior jugular
vein (nodi lymphoidei cervicales anteriores superficiales) and deep vessels
(nodi lymphoidei cervicales anteriores profundi) on the middle cricothyroid
ligament as well as ventral to the trachea.
nodi lymphoidei cervicales anteriores superficiales / superficial anterior
cervical lymph nodes : lymph nodes along the external jugular vein
as it emerges from the parotid gland, being superficial to the sternocleidomastoid
muscle; they receive afferent vessels from the auricle and parotid region.
nodi lymphoidei cervicales anteriores profundi / deep anterior cervical
lymph nodes : a group of numerous large lymph nodes that form a chain
along the internal jugular vein, extending from the base of the skull to
the root of the neck, situated near the pharynx, esophagus, and trachea;
they receive lymph from both superficial and deep structures.
nodi lymphoidei infrahyoidei / infrahyoid lymph nodes : lymph nodes
lying beneath the deep cervical fascia anterior to the thyrohyoid membrane
that receive lymph from the anterior cervical nodes and epiglottic region
and drain into the deep cervical nodes.
nodi lymphoidei prelaryngeales / nodi lymphoidei prelaryngei / prelaryngeal
lymph nodes : deep anterior cervical lymph nodes situated in front
of the larynx that help drain the thyroid gland.
nodi lymphoidei pretracheales / pretracheal lymph nodes : deep anterior
cervical lymph nodes situated in front of the trachea near the inferior
thyroid veins that helps drain the thyroid gland.
nodi lymphoidei paratracheales / paratracheal lymph nodes : lymph
nodes on either side of the esophagus, extending upward into the neck,
which receive lymph from the esophagus, trachea, and tracheobronchial lymph
nodi lymphoidei thyroidei / thyroid lymph nodes : deep anterior
cervical lymph nodes situated around the thyroid gland.
Delphian node : a lymph node encased in the fascia in the midline,
just anterior to the thyroid isthmus, so called because it is exposed first
at surgery and, if diseased, is indicative of disease in the thyroid gland,
but not of a specific disease process.
upper limb lymph nodes
nodi lymphoidei profundi membri superioris / deep lymph nodes of upper
limb : the lymph nodes situated internal to the deep fascia of the
upper limb, most of which are grouped in the axilla; they accompany the
radial, ulnar, interosseous, and brachial arteries and end in the brachial
axillary lymph nodes.
axillary lymph centre /
nodi lymphoidei axillares / axillary lymph nodes : the 20 to 30 lymph
nodes of the axilla, which receive lymph from all the lymph vessels of
the upper limb, most of those of the breast, and the cutaneous vessels
from the trunk above the level of the umbilicus (10÷60)
brachial or lateral group /
nodi lymphoidei brachiales / brachial lymph nodes / lateral axillary lymph
nodes : 4 to 6 axillary lymph nodes lying medial to, and behind, the
axillary vein, which drain most of the upper limb (4÷7)
or anterior group / nodi lymphoidei axillares pectorales / pectoral axillary
lymph nodes / nodi lymphoidei axillares anteriores / anterior axillary
lymph nodes : 4 or 5 axillary lymph nodes along the inferior border
of the pectoralis minor muscle near the lateral thoracic artery; they receive
lymph from the skin and muscles of the anterior and lateral thoracic walls
and mammary gland and drain into the central and apical nodes (3÷6)
subscapular or posterior
group / nodi lymphoidei axillares subscapulares / subscapular axillary
lymph nodes / nodi lymphoidei axillares posteriores / posterior axillary
lymph nodes : 6 or 7 axillary lymph nodes along the inferior margins
of the posterior axillary wall along the course of the subscapular artery;
they receive lymph from the skin and superficial muscles of the posterior
part of the neck and the posterior thoracic wall and drain into the apical
and central nodes (2÷6)
central group / nodi lymphoidei axillares
centrales / central lymph nodes : 3 or 4 axillary lymph nodes embedded
in adipose tissue near the base of the axilla; they receive lymph from
the lateral, pectoral, and subscapular nodes and drain into the apical
subclavicular or apical
group / nodi lymphoidei axillares apicales / apical lymph nodes : 6
to 12 axillary lymph nodes partly posterior to the superior part of the
pectoralis minor muscle and partly in the apex of the axilla, receiving
afferent vessels that accompany the cephalic vein and draining all other
axillary nodes; their efferent vessels unite to form the subclavian trunk.
nodi lymphoidei superficiales membri superioris / superficial
lymph nodes of upper limb : the lymph nodes of the upper limb that
are superficially placed; all except those in the hand and on the back
of the forearm converge toward and accompany the superficial veins
nodi lymphoidei cubitales / cubital lymph nodes / epitrochlear lymph
nodes : 1 or 2 superficially placed lymph nodes situated above the
medial epicondyle, medial to the basilic vein, the efferent vessels of
which accompany the basilic vein and join the deep lymph vessels
nodi lymphoidei supratrochleares / supratrochlear lymph nodes :
1 or 2 lymph nodes superficial to the deep fascia proximal to the medial
epicondyle and medial to the basilic vein and draining into the deep lymph
chest lymph nodes
parietal lymph nodes
nodi lymphoidei parasternales / parasternal lymph nodes (6÷10)
: nodes located along the course of the internal thoracic artery, which
drain the mammary gland, abdominal wall, and diaphragm.
nodi lymphoidei intercostales / intercostal lymph nodes : lymph
nodes in the back of the thorax, along the intercostal vessels (2÷3
per intercostal space)
anterior diaphragmatic lymph nodes
subscapular lymph nodes :
the 5 to 7 lymph nodes extending along the subscapular veins at the lower
border of the axilla, which drain the skin and muscles of the dorsal posterior
shoulder region and lower part of the back of the neck.
nodi lymphoidei deltopectorales / deltopectoral lymph nodes / nodi lymphoidei
infraclaviculares / infraclavicular nodes : 1 or 2 lymph nodes in the
groove between the pectoralis major and deltoid muscles, just inferior
to the clavicle, which drain into the apical lymph nodes
nodi lymphoidei interpectorales / interpectoral lymph nodes : small
inconstant lymph nodes that may occur between the mammary gland and apical
nodi lymphoidei paramammarii / paramammary lymph nodes : lymph nodes
on the lateral mammary gland that drain into the axillary lymph nodes.
visceral lymph nodes
anterior mediastinic lymph nodes
right or prevascular anterior mediastinic lymph nodes
left or preaorticocarotideal anterior mediastinic lymph nodes
transverse chain anterior mediastinic lymph nodes
diaphragmatic anterior mediastinic lymph nodes
nodus lymphoideus ligamenti arteriosi / lymph node of ligamentum arteriosum
: the lowest anterior mediastinal lymph node situated anterior to the ligamentum
posterior mediastinic lymph nodes (8÷12)
nodi lymphoidei juxtaoesophageales / juxtaesophageal lymph nodes
: posterior mediastinal lymph nodes situated on both sides of the esophagus.
nodi lymphoidei tracheobronchiales inferiores / inferior tracheobronchial
lymph nodes : nodes in the angle of the bifurcation of the trachea,
receiving lymph from adjacent structures.
nodi lymphoidei tracheobronchiales superiores / superior tracheobronchial
lymph nodes : nodes between the trachea and the bronchus on either
side, receiving lymph from adjacent structures (5÷7)
tracheal road fork lymph nodes (9÷12)
nodi lymphoidei bronchopulmonales / bronchopulmonary lymph nodes / hilar
lymph nodes and nodi lymphatici hilares : lymph nodes embedded in the
root of the lung, mainly at the hilum that drain into the tracheobronchial
nodi lymphoidei intrapulmonales / intrapulmonary lymph nodes / nodi
lymphoidei pulmonales / pulmonary lymph nodes : nodes located along
the larger bronchi within the lung substance, through which lymph from
the lung drains
nodus lymphoideus arcus venae azygos / lymph node of arch of azygos
vein : a lymph node sometimes present on the azygos vein at the point
where it arches over the root of the lung.
nodi lymphoidei prepericardiaci / nodi lymphoidei prepericardiales /
prepericardial lymph nodes : lymph nodes situated between the pericardium
nodi lymphoidei prevertebrales / prevertebral
lymph nodes : lymph nodes situated in back of the thoracic aorta.
nodi lymphoidei phrenici superiores / superior phrenic lymph nodes
: several nodes on the thoracic surface of the diaphragm, receiving lymph
from the intercostal spaces, pericardium, diaphragm, and liver; called
also diaphragmatic lymph nodes.
abdominal lymph nodes
nodi lymphoidei abdominis parietales / parietal
abdominal lymph nodes : the lymph nodes that drain the abdominal walls,
left lymph nodes
intermediate lymph nodes
lumbar, aortic or lumboaortic
lymph nodes (20÷30 ?) : numerous large lymph nodes extending
from the aortic bifurcation to the aortic hiatus of the diaphragm, as 3
parallel chains: left, intermediate, and right
nodi lymphoidei lumbales dextri / right lumbar lymph nodes / nodi lymphatici
lumbares dextri : the chain of lumbar lymph nodes situated partly in
front of the vena cava and partly behind it on the psoas major muscle
nodi lymphoidei cavales laterales / lateral caval lymph nodes :
a group of lymph nodes of the right lumbar group that are on the right
side of the inferior vena cava.
nodi lymphoidei precavales / precaval
lymph nodes : a group of lymph nodes of the right lumbar group that
is in front of the inferior vena cava.
nodi lymphoidei retrocavales / retrocaval lymph nodes / postcaval lymph
nodes / nodi lymphoidei postcavales : a group of lymph nodes of the
right lumbar group situated behind the inferior vena cava
nodi lymphoidei lumbales intermedii / intermediate lumbar lymph nodes
/ nodi lymphatici lumbares intermedii / paraaortic
lymph nodes : the chain of lumbar lymph nodes that lie in the median
plane, between the left and right lumbar lymph nodes
nodi lymphoidei lumbales sinistri / left lumbar lymph nodes / nodi lymphatici
lumbares sinistri : the chain of lumbar lymph nodes situated at the
side of the abdominal aorta on the psoas major muscle, comprising 3 groups:
nodi lymphoidei mesenterici / mesenteric lymph nodes (MLN) : nodes
that lie at the root of the mesentery, receiving lymph from parts of the
small intestine, cecum, appendix, and large intestine (130÷150)
nodi lymphoidei mesenterici inferiores / inferior mesenteric lymph nodes
: nodes situated along the inferior mesenteric vessels and receiving lymph
from the adjacent region; they comprise two groups: the sigmoid and superior
rectal lymph nodes.
nodi lymphoidei sigmoidei / sigmoid lymph nodes : a group of lymph
nodes of the inferior mesenteric group, situated along the sigmoid arteries.
nodi lymphoidei mesenterici juxtaintestinales / juxtaintestinal mesenteric
lymph nodes : the mesenteric lymph nodes situated close to the wall
of the intestine between the branches of the jejunal and ileal arteries;
they drain into the superior mesenteric lymph node.
nodi lymphoidei mesenterici superiores / superior mesenteric lymph nodes
: mesenteric lymph nodes situated along the superior mesenteric artery
and draining various other groups of nodes in the region.
nodi lymphoidei mesenterici superiores centrales / central superior
mesenteric lymph nodes : the middle group of superior mesenteric nodes,
situated along the ileal and jejunal branches of the superior mesenteric
nodi lymphoidei mesocolici / mesocolic lymph nodes : lymph nodes
situated in the mesocolon; they drain through the superior mesenteric lymph
nodi lymphoidei colici dextri/medii/sinistri / colic lymph nodes
: a subgroup of the mesocolic lymph nodes, situated along the right, middle,
and left colic arteries.
nodi lymphoidei paracolici / paracolic lymph nodes : a subgroup
of the mesocolic lymph nodes, situated along the medial borders of the
ascending and descending colon and along the mesenteric borders of the
transverse and sigmoid colon.
paracardial lymph nodes : a group of small lymph nodes forming a
chain or ring (annulus lymphaticus cardiae), around the cardiac
opening of the stomach.
nodi lymphoidei gastrici dextri/sinistri / right/left gastric lymph
nodes : a few nodes along the right and left gastric arteries that
receive lymph from the stomach, spleen, duodenum, liver, and pancreas.
nodi lymphoidei hepatici / hepatic lymph nodes : a variable number
of lymph nodes situated along the proper and common hepatic arteries and
the bile ducts that receive lymph from the stomach, spleen, duodenum, liver,
and pancreas (3÷6)
nodus lymphoideus foraminalis / foraminal lymph node / node of anterior
border of epiploic foramen / node of epiploic foramen : a hepatic lymph
node situated along the upper part of the common bile duct
nodus lymphoideus cysticus / cystic lymph node / node of neck of gallbladder
: a hepatic lymph node situated in the curve of the neck of the gallbladder
at the junction of the cystic and common hepatic ducts
pancreaticolienal lymph nodes (8÷10)
right and left lateral aortic
nodi lymphoidei retroaortici / retroaortic
lymph nodes / postaortic lymph nodes / nodi lymphoidei postaortici
: a group of lymph nodes of the left lumbar group, situated behind the
aorta and formed by peripheral nodes of the right and left lateral aortic
lymph nodes (4÷5)
nodi lymphoidei preaortici / preaortic
lymph nodes : a group of lymph nodes of the left lumbar group that
is in front of the aorta and drains the abdominal part of the alimentary
canal and its derivatives.
terminal colic lymph nodes : lymph nodes associated with the main
trunks of the superior and inferior mesenteric arteries, being continuous
with the corresponding preaortic lymph nodes.
epicolic lymph nodes : minute lymph nodes situated on the wall of
the bowel and sometimes in the epiploic appendices.
nodi lymphoidei phrenici inferiores / inferior phrenic lymph nodes
: parietal lymph nodes accompanying the inferior vessels of the diaphragm.
nodi lymphoidei epigastrici inferiores / inferior epigastric lymph nodes
: lymph nodes along the deep epigastric vessels, receiving lymph from the
lower abdominal wall.
nodi lymphoidei abdominis viscerales / visceral
abdominal lymph nodes : the numerous lymph nodes that drain the abdominal
nodi lymphoidei aortici laterales / lateral aortic lymph nodes :
2 chains (right and left) of the left lumbar group that are on the left
side of the aorta and drain the suprarenal glands, kidneys, ureters, testes,
ovaries, pelvic viscera (except the intestines), and posterior abdominal
nodi lymphoidei pylorici / pyloric lymph nodes : lymph nodes found
anterior to the head of the pancreas, receiving lymph from the pyloric
part of the stomach. They are subdivided into 3 groups:
nodus lymphoideus suprapyloricus / suprapyloric lymph node : a pyloric
lymph node located superior to the duodenum on the right gastric artery.
nodi lymphoidei subpylorici / subpyloric lymph nodes : pyloric lymph
nodes located inferior to the pylorus.
nodi lymphoidei retropylorici / retropyloric lymph nodes : pyloric
lymph nodes situated posterior to the pylorus.
nodi lymphoidei pancreatici / pancreatic lymph nodes : nodes found
along the pancreatic arteries that drain lymph from the pancreas to the
pancreaticosplenic lymph nodes.
nodi lymphoidei pancreatici inferiores / inferior pancreatic lymph nodes
: lymph nodes associated with the inferior pancreatic artery.
nodi lymphoidei pancreatici superiores / superior pancreatic lymph nodes
: lymph nodes associated with the superior pancreatic artery.
nodi lymphoidei pancreaticoduodenales inferiores / inferior pancreaticoduodenal
lymph nodes : lymph nodes situated along the inferior pancreaticoduodenal
nodi lymphoidei pancreaticoduodenales superiores / superior pancreaticoduodenal
lymph nodes : lymph nodes situated along the superior pancreaticoduodenal
nodi lymphoidei coeliaci / celiac lymph nodes : a few nodes along
the celiac trunk, which receive lymph from the stomach, spleen, duodenum,
liver, and pancreas.
nodi lymphoidei splenici / splenic lymph nodes : lymph nodes in
the capsule and larger trabeculae of the spleen that drain into adjacent
lymph nodes; called also nodi lymphoidei lienales
nodi lymphoidei gastroomentales dextri/sinistri / right/left gastroomental
lymph nodes / nodi lymphatici gastroepiploici dextri/sinistri / right/left
gastroepiploic lymph nodes : lymph nodes situated in the greater omentum
along the pyloric half of the greater curvature of the stomach in association
with the right and left gastroepiploic arteries
nodi lymphoidei appendiculares / appendicular lymph nodes : lymph
nodes situated along the appendicular artery and in the mesoappendix that
drain into the ileocolic lymph nodes.
nodi lymphoidei precaecales / prececal lymph nodes : lymph nodes
situated in front of the cecum that drain into the anterior ileocolic lymph
nodi lymphoidei retrocaecales / retrocecal lymph nodes : lymph nodes
situated in back of the cecum that drain into the posterior ileocecal lymph
nodi lymphoidei rectales superiores / superior rectal lymph nodes
: a group of lymph nodes of the inferior mesenteric group, situated along
the superior rectal artery.
pelvic lymph nodes
circumflex iliac lymph nodes : lymph nodes situated along the deep
iliac circumflex vessels.
nodi lymphoidei pelvis parietales / parietal
pelvic lymph nodes : the lymph nodes that drain the wall of the pelvis
nodi lymphoidei iliaci externi / external
iliac lymph nodes : the 8 to 10 nodes along the external iliac vessels;
they receive afferent vessels from the inguinal lymph nodes, deep part
of the abdominal wall below the umbilicus, and some pelvic viscera and
send efferent vessels to the common iliac lymph nodes.(6÷10)
nodi lymphoidei iliaci externi intermedii / intermediate external iliac
lymph nodes : the external iliac lymph nodes situated between the external
nodi lymphoidei iliaci externi laterales / lateral external iliac lymph
nodes : the external iliac lymph nodes situated on the lateral aspect
of the external iliac vessels.
nodi lymphoidei iliaci externi mediales / medial external iliac lymph
nodes : the external iliac lymph nodes situated on the medial aspect
of the external iliac vessels.
nodi lymphoidei interiliaci / interiliac lymph nodes : the external
iliac lymph nodes situated between the external and internal iliac vessels
and the obturator artery.
nodi lymphoidei obturatorii / obturator
lymph nodes : the external iliac lymph nodes situated in the obturator
nodi lymphoidei iliaci interni / internal
iliac lymph nodes : nodes grouped around the origins of the branches
of the internal iliac vessels; they receive afferent vessels from the pelvic
viscera, perineum, and buttocks and send efferent vessels to the common
iliac lymph nodes (10÷12)
nodi lymphoidei gluteales inferiores / inferior gluteal lymph nodes
: the internal iliac lymph nodes situated along the inferior gluteal artery.
nodi lymphoidei gluteales superiores / superior gluteal lymph nodes
: the internal iliac lymph nodes situated along the superior gluteal artery.
nodi lymphoidei sacrales / sacral lymph nodes : the internal iliac
lymph nodes situated along the lateral and median sacral vessels; they
receive lymph from the rectum and posterior pelvic wall.
nodi lymphoidei iliaci communes / common
iliac lymph nodes : the 4 to 6 lymph nodes grouped at the sides and
dorsal to the common iliac vessels; they receive afferent vessels from
the lateral and internal iliac lymph nodes and send efferent vessels to
the lateral aortic lymph nodes (8÷10)
nodi lymphoidei iliaci communes intermedii / intermediate common iliac
lymph nodes : the common iliac lymph nodes situated between the common
nodi lymphoidei iliaci communes laterales / lateral common iliac lymph
nodes : the common iliac lymph nodes situated on the lateral aspect
of the common iliac vessels.
nodi lymphoidei iliaci communes mediales / medial common iliac lymph
nodes : the common iliac lymph nodes situated on the medial aspect
of the common iliac vessels.
nodi lymphoidei iliaci communes promontorii / promontory common iliac
lymph nodes : the common iliac lymph nodes situated in front of the
nodi lymphoidei iliaci communes subaortici / subaortic common iliac
lymph nodes : the common iliac lymph nodes situated below the bifurcation
of the aorta
nodi lymphoidei pelvis viscerales / visceral
pelvic lymph nodes : the lymph nodes that drain the pelvic viscera
nodi lymphoidei parauterini / parauterine lymph nodes : lymph nodes
situated around the uterus, consisting of superficial (beneath the peritoneum)
and deep (in the substance of the uterine wall) nodes: they drain into
the lumbar, external and internal iliac, sacral, and superficial inguinal
nodi lymphoidei paravaginales / paravaginal lymph nodes : lymph
nodes situated around the vagina; they drain into the external and internal
iliac, common iliac, and superficial inguinal lymph nodes.
nodi lymphoidei paravesicales / paravesicular lymph nodes : lymph
nodes situated around the urinary bladder; they drain into the external
and internal iliac lymph nodes and, in association with some lymph nodes
from the prostate, into the sacral and common iliac lymph nodes.
nodi lymphoidei vesicales laterales / lateral vesicular lymph nodes
: the paravesicular lymph nodes situated in relation to the lateral umbilical
nodi lymphoidei prevesicales / prevesicular lymph nodes : the paravesicular
lymph nodes situated in front of the urinary bladder.
nodi lymphoidei retrovesicales / retrovesicular lymph nodes / postvesicular
lymph nodes / nodi lymphoidei postvesicales : the paravesicular lymph
nodes situated in back of the urinary bladder
nodi lymphoidei pararectales / pararectal lymph nodes / anorectal lymph
nodes / nodi lymphoidei anorectales : lymph nodes situated around the
rectum, embedded in its muscular coat; they drain into the inferior mesenteric,
sacral, internal iliac, common iliac, and superficial inguinal nodes
nodus lymphoideus lacunaris intermedius / intermediate lacunar lymph
node : a lymph node situated between the external iliac vessels at
the lacuna vasorum
nodus lymphoideus lacunaris lateralis / lateral lacunar lymph node
: a lymph node situated on the lateral aspect of the external iliac vessels
at the lacuna vasorum.
nodus lymphoideus lacunaris medialis / medial lacunar lymph node
: a lymph node situated on the medial aspect of the external iliac vessels
at the lacuna vasorum.
lower limb lymph nodes
nodus lymphoideus tibialis anterior / anterior tibial lymph node
: a lymph node situated along the anterior tibial artery.
nodus lymphoideus tibialis posterior / posterior tibial lymph node
: a lymph node situated along the posterior tibial artery.
small peronier lymph nodes
nodus lymphoideus fibularis / fibular lymph node / peroneal lymph node
: a lymph node situated along the peroneal artery
nodi lymphoidei poplitei / popliteal lymph nodes : lymph nodes embedded
in the fat of the popliteal fossa; their efferent vessels accompany the
femoral vessels to the deep inguinal lymph nodes.(4÷6)
nodi lymphoidei poplitei profundi / deep popliteal lymph nodes :
the popliteal lymph nodes situated at the sides of the popliteal vessels.
nodi lymphoidei poplitei superficiales / superficial popliteal lymph
nodes : the popliteal lymph nodes situated at the termination of the
small saphenous vein.
inguinal lymph centre / inguinal
nodi lymphoidei inguinales superficiales / superficial
inguinal lymph nodes : lymph nodes situated in the subcutaneous tissue
inferior to the inguinal ligament on either side of the proximal part of
the greater saphenous vein; they drain the skin of the lower abdominal
wall, penis, scrotum or labia majora, perineum, and buttocks (15÷20)
nodi lymphoidei inguinales superficiales inferiores / inferior superficial
inguinal lymph nodes : the lower superficial inguinal lymph nodes situated
below the opening of the saphenous vein.
nodi lymphoidei inguinales superficiales superolaterales / superolateral
superficial inguinal lymph nodes : the upper superficial inguinal nodes
situated on the lateral side of the opening of the saphenous vein.
nodi lymphoidei inguinales superficiales superomediales / superomedial
superficial inguinal lymph nodes : the upper superficial inguinal lymph
nodes situated on the medial side of the opening of the saphenous vein.
nodi lymphoidei inguinales profundi / deep inguinal lymph nodes
: nodes deep to the fascia lata along the femoral vein; they receive lymph
from the deep structures of the lower limb and from the penis or clitoris,
and superficial inguinal lymph nodes and drain into the external iliac
lymph nodes (1÷8)
Cloquet's node / node of Cloquet :
the highest of the deep inguinal lymph nodes
spleen (see also diseases
: 80-300 g (highest between age 25-35 years); from foetal week 12 up to
foetal week 38 and in some diseases it sustains hemopoiesis.
14-40% of individuals has small accessory
in epiploon retrocavity. In addition to capturing Ags from the blood that
passes through the spleen, migratory macrophages and DCs bring Ags to the
spleen via splenic artery(there
are no lymph vessels in parenchyma !), triggering immune responses.
Capsular septa are short and don't divide spleen into lobes => no contractility.
It contains 40 ml of blood and 33% of the platelets produced by bone marrow,
and clears 20 ml of erythrocytes a day. See also splenic
From the examinations performed on 38 individuals it was possible to determine
a mean value of 11.1 cm for the craniocaudal extent of the spleen,
11.8 cm for the anatomical length of the spleen, 10.4 cm for the
width of the spleen, and 4.2 cm for the thickness of the spleenref.
trabeculae splenicae / trabeculae of spleen / trabeculae lienis
: fibrous bands that pass into the spleen from the tunica fibrosa and form
the supporting framework of the organ
trabecular veins : vessels coursing in splenic trabeculae, formed
by tributary pulp veins.
facies colica splenis or lienis : the surface of the spleen in contact
with the colon
facies gastrica splenis or lienis : the surface of the spleen in
contact with the stomach
It can be functionally divided into :
red pulp (RP) : capillaries can open
tissue (free blood cells form Billroth cords, representing a blood
reserve: open circle (90%))
directly into sinus of spleen / splenic
sinus / sinus splenicus / sinus lienalis (a dilated venous sinus not
lined by ordinary endothelial cells) (closed circle (10%)).
Macrophages surrounding ellipsoid or sheathed arteries or arterioles
(arterial branches having spindle-shaped thickenings in their walls and
forming the penicilli of the spleen) form the Schweigger-Seidel sheaths,
which remove old/defective/opsonized blood cells (hemocatheresis
marginal zone (MZ) sinus
: memory function; at least a major number of human splenic CD27+
MZ B cells are migratory. Phenotypic data suggest a recirculation pathway
between the spleen and mucosal tissues in humansref
white pulp (WP) is structurally similar
to a lymph node, although the spleen receives
antigen directly from the blood and not through afferent lymphatics. It
consists of :
marginal zone (MZ). It is made up of
and secondary lymphoid follicles (see above
for lymph nodes), containing
marginal zone B cells (MZB).
The origin of marginal-zone B cells is debated, and probably includes post-GC
memory B cells and naive B cells involved in T-cell-independent immune
Depletion of MZM can be experimentally induced by administration of clodronate
encapsulated in liposomes.
The marginal zone is a B-cell-rich zone located between B-cell follicles
and the T-cell area in the spleen (a similar region is present in Peyer’s
patches, but usually not in lymph nodes)
sheath (PALS) / noduli lymphoidei splenici / splenic lymphoid nodules /
noduli lymphoidei lienales / folliculi lymphatici splenici / folliculi
lymphatici lienales : aggregations of lymphatic tissue that ensheath
the arteries in the spleen. Together with the artery itself it is named
lienal nodule / malpighian bodies or corpuscles of spleen), in which
you can distinguish ...
B cell zones (BCZ) : B cells appear
at pregnancy month 3, while first plasma cells appear at pregnancy month
NK cells represent 5÷15% of all spleen lymphocytes
Similar to the lymph node, the spleen has a conduit system consisting of
a tubular network containing collagen fibres that are surrounded by reticular
fibroblast. The white pulp is known to restrict cellular movement to lymphocytes
and DCs, but the conduit also limits the entry of large molecules. Locally
produced chemokines are also found in the conduit area : CCL21
in the T-cell area and CXCL13 / BLC
in the B-cell area. Theories explaining how the blood in the spleen gets
from the arteries to the venous sinuses :
open or slow circulation theory holds that the capillaries open
directly into the pulp reticulum, and that the blood gradually filters
back into the venous sinuses
closed or fast circulation theory holds that the capillaries empty
directly into the venous sinuses
closed-open circulation theory : the theory that both an open and
a closed circulation are present in the spleen; e.g., a closed circulation
in a contracted spleen may become an open circulation when the organ is
penicilli arteriae lienalis
/ penicilli arteriae splenicae : brushlike groups of arterial branches
of the lobules of the spleen
artery of the pulp : a name given the first portion of one of the
penicilli arteriae splenicae
lymphoid tissue (MALT) (O-MALT) in lamina propria and submucosal tonaca
of epithelia. It contains intraepithelial lymphocytes (IELs : mostly
that recircle around blood and different MALTs : such a "common mucosa"
theory is used by vaccines
targeting mucosal immunity but immune responses at the site of induction
is stronger than at distant sites and the urogenital tract seem to function
more independently than others. Anyway common mucosal immunity can be efficiently
induced in mice following immunization through the skin with vaccine formulations
chemical agents capable of locally enhancing cAMP levels, or exposure of
skin to UVBRef.
traffic patterns, regulated by selective expression of adhesion proteins
in peripheral or mucosal lymphatic tissues, maintain anatomic segregation
of immunological memory by causing Ag-primed cells to return to specific
anatomic destinations where they will encounter conditions that further
facilitate expression of peripheral or mucosal immunity. Among potentially
myriad factors, these conditions include prevalence of specific cytokines,
adhesion to- and costimulation by specific stromal cells, and still unknown
microenvironmental factors intrinsic to those lymphoid compartments that
favor commitment of B cells to specific Ig isotypes or T cells to peripheral
or mucosal immunity. MALT plasma cells produce mainly IgA
dimers and IgM
pentamers. As neither phagocytes nor killer cells nor complement
factors are available on the external side of the epithelial barrier, the
only biological activity of secretory antibodies is neutralization of the
biological activity of the antigen by competitive binding (e.g.
prevent absorption of viruses, Bacteria and toxins by blocking their
adhesion), enabling them to be flushed away in the stream of secreted
fluids and mucous washing over the epithelial membranes. IgA may
also facilitate transport of pathogens and toxins out of the body by causing
them to be conveyed into bile and other exocrine secretions. Ag-specific
IgA has been shown to neutralize viral pathogens during transport across
of Peyer's patches, where nondegradative endosomal transport might otherwise
deliver a pathogen into the host. Fc
receptor-like 4 (FCRL4) / immunoglobulin superfamily receptor translocation-associated
1 (IRTA1) is a novel surface B-cell receptor related to Fc receptors,
inhibitory receptor superfamily (IRS), and cell adhesion molecule (CAM)
family members selectively and consistently expressed by a B-cell population
located underneath and within the tonsil epithelium and dome epithelium
of Peyer patches (regarded as the anatomic equivalents of marginal
zone of spleen). Similarly, in mucosa-associated
lymphoid tissue (MALT) lymphomas
IRTA1 was mainly expressed by tumor cells involved in lympho-epithelial
lesions. In contrast, no or a low number of IRTA1+ cells was
usually observed in the marginal zone of mesenteric lymph nodes and spleen.
Interestingly, monocytoid B cells in reactive lymph nodes were strongly
IRTA1+. Tonsil IRTA1+ cells expressed the memory
B-cell marker CD27 but not mantle cell-, germinal center-, and plasma cell-associated
molecules. PCR analysis of single tonsil IRTA1+ cells showed
they represent a mixed B-cell population carrying mostly mutated, but also
unmutated, IgV genes. The immunohistochemical finding in the tonsil epithelial
areas of aggregates of IRTA1+ B cells closely adjacent to plasma
cells surrounding small vessels suggests antigen-triggered in situ
proliferation/differentiation of memory IRTA1+ cells into plasma
cells. Collectively, these results suggest a role of IRTA1 in the immune
function of B cells within epitheliaref.
CD8ab+ and CD8ab-CD8aa
acquire gut tropism and a memory phenotype after non-self antigen stimulation
by Peyer's patch and mesenteric lymph node (MLN) DCs and have effector/CTL
CD4+ and CD4+CD8aa+ acquire
gut tropism and a memory phenotype after non-self antigen stimulation by
Peyer's patch and MLN DCs and have effector/help function
natural memory ab-TcR+ T cells :
DN and CD8aa+ acquire gut tropism
and a memory phenotype after self-antigen selection in the thymus and have
effector and/or regulatory functions
: DN and CD8aa+ acquire gut tropism
and differentiation during ontogeny and have tissue repair and regulatory
The majority of iIELs express the cytotoxic CD8+ phenotype, either as a
CD8aa homodimer or a CD8ab
heterodimer. NK-like cytotoxicity of iIELs partly depends on CD4-CD8aa+
and CD4-CD8- iIELs and TcR-
Cell death program of IECs is regulated by self-produced IL-15
through the activation of intraepithelial NK cells.
a myeloid-derived mucosal DC in mice populates the entire lamina propria
of the small intestine. Lamina propria DCs were found to depend on the
chemokine receptor CX3CR1
to form transepithelial dendrites, which enable the cells to directly sample
luminal antigens. CX3CR1 was also found to control the clearance
of entero-invasive pathogens by DCs. Thus, CX3CR1-dependent
processes, which control host interactions of specialized DCs with commensal
and pathogenic bacteria, may regulate immunological tolerance and inflammationref.
nasopharyngeal lymphoid system orWaldeyer's
ring : Storr pores allows a wide contact surface on tonsillar
cryptae. Tonsils / tonsillae (small rounded mass of lymphoid tissue)
tonsil / adenoid tonsil / tonsilla adenoidea / tonsilla pharyngea or pharyngealis
/ third tonsil : the diffuse lymphoid tissue and follicles in the roof
and posterior wall of the nasopharynx
noduli lymphoidei tonsillae pharyngealis / lymphoid nodules of pharyngeal
tonsils : small collections of lymphoid tissue associated with the
Gerlach's tubal tonsils / tonsilla
tubaria / eustachian tonsil / tonsil of torus tubarius : a collection
of lymphoid tissue associated with the pharyngeal opening of the auditory
palatine tonsils or amygdalae
/ tonsilla palatina / faucial tonsil : either of 2 small, almond-shaped
masses located between the palatoglossal and palatopharyngeal arches, one
on either side of the oropharynx, composed mainly of lymphoid tissue, covered
with mucous membrane, and containing various crypts and many lymph follicles
submerged tonsil : a palatine tonsil that is shrunken and atrophied
and is partly or entirely hidden by the palatoglossal arch
lingual tonsil / tonsilla lingualis
: an aggregation of lymph follicles on the floor of the oropharyngeal passageway,
at the root of the tongue.
noduli lymphoidei tonsillae lingualis / lymphoid nodules of lingual
tonsil / folliculi linguales / lingual follicles : lymphoid nodules
on the root of the tongue, associated with the lingual tonsil
laryngeal tonsil in tunica propria
of upper part of ventriculus laryngis Morgagnii
inductive sites : the enteric bacterial flora appears to be the
major stimulus for the development of the mucosal immune system, as reflected
by the death of MALT in adult germfree animals. When germfree animals are
given an intestinal flora, their MALT greatly expands along the length
of intestine and secretory IgA
is produced in quantity. Some bacteria are more effective than others when
given to germfree mice in inducing the GC reactions in PPs, stimulating
IgA plasma cells in the lamina propria. Intestine develops immunological
to Ags of enteric bacterial flora, i.e., intestinal lymphocytes do not
proliferate when stimulated with Ags of their own intestinal bacteria but
do proliferate when stimulated with Ags of intestinal bacteria isolated
from other humans.
noduli lymphoidei aggregati intestini
tenuis / aggregated lymphoid nodules of small intestine / ilealPeyer's
patches (PP)(IPP) / Peyer's glands or plaques / noduli lymphatici
aggregati [peyeri] : oval elevated areas of lymphoid tissue on the
mucosa of the small intestine, composed of ...
many lymphoid follicles closely packed together. The dome epithelium
of PP is regarded as the anatomic equivalents of marginal
zone of spleen
noduli lymphoidei solitarii / isolated
lymphoid follicles (ILF) / solitary lymphatic or lymphoid nodules / noduli
lymphatici solitarii / folliculi lymphatici solitarii / solitary lymphatic
or lymphoid follicles : small concentrations of lymphoid tissue scattered
throughout the mucosa and submucosa of the small and large intestines
effector sites (lamina propria)
noduli lymphoidei aggregati appendicis vermiformis / aggregated
lymphoid nodules of vermiform appendix / folliculi lymphatici aggregati
processus vermiformis : oval elevated areas of lymphoid tissue occupying
the greater part of the submucosa of the appendix
It is anatomically equivalent to avian bursa
(whose functional equivalent is hematopoietic
bone marrow). If the human appendix functions as a primary lymphoid
organ, it may occur during the early development, when GC T cell density
lymphoid tissue (BALT) is occasionally found in the upper bronchi of
some species (mice and humans) and is induced by an antigen-independent
: it contains significant numbers of normal IgD-secreting
plasma cells due to activation by OMPs from colonizing Moraxella
and Haemophilus influenzae.
noduli lymphatici bronchiales : lymph nodules situated in
the lining of the bronchi.
induced BALT (iBALT) : although
the presence of BALT in mouse and human lungs is controversial, there are
reports that infection or inflammation triggers the organization of lymphoid
structures in the lungs of both speciesref1,
These structures do not fit the classical definition of BALT, as they are
not formed independently of antigenref1,
(Plesch, B.E.C., van der Brugge-Gamelkoorn, G.J. & van de Ende, M.B.
Development of bronchus associated lymphoid tissue (BALT) in the rat, with
special reference to T and B cells. Dev. Comp. Immunol. 7, 79–84 (1983).
). Because inducible BALT (iBALT) appears in the lung only after
infection or inflammation, it is generally assumed that iBALT is simply
an accumulation of effector cells that were initially primed in conventional
lymphoid organs; however, it is also possible that inflammatory responses
directly trigger the neo-formation of iBALT, which promotes the recruitment,
priming and expansion of antigen-specific lymphocytes in situ. Thus,
iBALT may functionally replace conventional lymphoid organs in respiratory
immune responses. A fundamental tenet of immunology is that primary adaptive
immune responses are initiated in secondary
lymphoid organs, such as lymph nodes,
patches or spleenref1,
These lymphoid organs are organized to recruit naive lymphocytes from the
blood and to promote their interaction with activated antigen-presenting
cells from surrounding tissuesref.
Once lymphocytes have been activated and clonally expanded in centralized
lymphoid organs, the resulting effector cells localize to the infected
or inflamed tissues and perform their effector functionsref.
For example, B and T cells responding to influenza
are first detected in the lymph nodes that drain the respiratory tract,
and are only later found in the lungref.
Consistent with an essential role for lymphoid organs in primary immune
responses, splenectomized lymphotoxin--null (Lta-/-)
or alymphoplastic (aly/aly, also known as Map3k14-/-)
— which lack spleen, lymph nodes and Peyer's patches — are unable to generate
primary immune responses to a variety of pathogensref,
However, Lta-/- mice infected with respiratory viruses
are capable of generating antigen-specific B and T cellsref1,
albeit with delayed kinetics, suggesting that lymphocytes can also be primed
in non-lymphoid tissues. Consistent with this idea, the bone marrow seems
to function as an alternative site of lymphocyte priming to systemic antigens
when lymph nodes are unavailableref1,
Another tissue that facilitates primary immune responses to respiratory
infections is the BALTref.
Lymphoid structures, complete with B cell follicles, germinal centers,
and T cell zones, form in the lung in response to influenza infectionref.
This finding casts new light on respiratory immunity, showing that it is
more self-contained than previously thought. These data are consistent
with published reports showing that T cells can be primed directly in the
Therefore, it is somewhat surprising that iBALT is often overlooked as
an inductive site for immune responses to respiratory infections, particularly
as GCB cells and iBALT are easily detected in the lungs of normal mice.
The most probable explanation for this oversight is that immune responses
initiated in iBALT are delayed relative to the immune response in the draining
lymph nodes, owing to the time it takes to form iBALT. Therefore, immune
responses initiated in iBALT of normal mice are obscured by the rapid
and robust responses initiated in conventional lymphoid organs. Notably,
other studies have shown that iBALT is particularly prominent after
multiple respiratory infectionsref.
iBALT induced by one infection will alter the kinetics and location of
subsequent immune responses to respiratory antigens. For example, the ability
of previous influenza infection to prevent tolerance induction by the intranasal
administration of ovalbumin may be the result, in part, of the presence
In addition, the formation of iBALT in chronic lung diseases, such as pulmonary
may be a component of the pathologyref.
Although the iBALT that develops after influenza infection resembles constitutive
BALT, it is distinct in that it is induced by inflammatory insult. In addition,
the size of iBALT varies widely, from small clusters of B cells, T cells
and DCs to well-developed follicular areas. Furthermore, unlike constitutive
BALT, iBALT is found in perivascular, peribronchial and even interstitial
areas in the lower airways of the lung, and does not always occur under
a dome epithelium. However, iBALT does contain B-cell follicles centered
around networks of FDCs, separated by interfollicular regions containing
DCs and T cells. High endothelial venules (HEVs) expressing PNAd are also
present in iBALT, allowing for the recruitment of naive T cellsref.
Thus, iBALT shares functional and structural characteristics with classically
However, whereas the development of secondary lymphoid organs — such as
nodes and Peyer's patches — and the
expression of CXCL13 / BLC
in the spleen are typically dependent on LTref1,
the formation of iBALT and the expression of CXCL13 and CCL21 in the lung
occur independently of LT. Similarly, germinal-center formation in the
lung, but not the spleen or NALT, is LT independent. Thus, the development
and organization of iBALT is governed by mechanisms that are distinct from
those that regulate the development and organization of conventional secondary
lymphoid organs. Notably, iBALT is often observed in the lungs of Lta-/-
mice that have not been intentionally infectedref.
A number of possibilities have been proposed to explain this phenomenon.
For example, the lack of IgE in Lta-/- mice may result
in respiratory inflammation and lymphocyte accumulation in the lungref.
In addition, the inability of Lta-/- mice to express
in the thymus may cause autoimmune inflammation in the lung and other tissuesref.
Alternatively, the constitutive expression of CCL21 in the lungs may result
in the enhanced recruitment of lymphocytes owing to the loss of CCL21 in
conventional lymphoid organsref.
Finally, it is possible that respiratory infection with opportunistic pathogens
may result in increased lymphocyte accumulation in the lungs of Lta-/-
mice. Lta-/- mice re-derived by embryo transfer and maintained
on antibiotics to prevent infection with Pneumocystis carinii
and other respiratory pathogens did not have significant infiltration in
the lungs of Lta-/- mice under the age of 4–5 months.
However, as these mice aged, accumulations of lymphocytes in the lungs
(particularly B cells) occurred. This may be the result of delayed colonization
of the lung by opportunistic pathogens or to other defects in Lta-/-
mice. Importantly, the possibility that the relatively normal respiratory
immune responses observed in SLP mice resulted from pre-existing iBALT
in Lta-/- recipient mice was eliminated by confirming
results with splenectomized Rorc-/- mice. As Rorc-/-
mice lack lymph nodes and Peyer's patchesref,
but express LT normally and do not spontaneously develop iBALT, they provided
an independent method to evaluate the requirement for spleen, lymph nodes
and Peyer's patches in respiratory immune responses. These experiments
showed that T- and B-cell responses were generated with near-normal to
normal kinetics in splenectomized Rorc-/ mice, and suggest
that any pre-existing lymphoid accumulations in the lungs of Lta-/-
recipient mice did not measurably influence results. Thus, the formation
of iBALT occurs as a normal component of the immune response to respiratory
infections and may also occur as a consequence of pathological inflammation
in the lung. One surprising outcome of these experiments was that iBALT
initiated immune responses that were not only protective, but resulted
in less morbidity and mortality than immune responses initiated in conventional
lymphoid tissues, probably simply a function of the reduced size of
the immune response at early times after infection in SLP mice. Although
the influenza-specific CD8+ T-cell response in SLP mice was
about 20% of WT levels on days 9 and 10, this was sufficient to substantially
lower the viral load in SLP mice. By day 14, when large numbers of T cells
were present in the lungs of SLP mice, virus was already eliminated, which
limited additional T-cell activation. Thus, the T-cell response in SLP
mice is limited at both early and late time points of infection. Because
activated T cells produce large quantities of TNF,
a reduced T-cell response in SLP mice should result in less weight loss
and morbidity. Therefore, the increased survival and reduced morbidity
of SLP mice is probably the result of 'just enough' immunity, which begins
to clear virus without the systemic production of pathologic levels of
cytokines. Together, these data alter our perception of how respiratory
immune responses occur in normal animals, and overturn the immunological
dogma that primary immune responses are generated only in constitutively
present secondary lymphoid organs. Secondary lymphoid organs, such as spleen
and lymph nodes, accelerate and amplify immune responses to antigens or
pathogens in peripheral tissues. Yet these lymphoid organs are not absolutely
required for immunity and may, under certain circumstances, facilitate
the development of overly robust and perhaps damaging immune responses.
However, smaller and possibly less pathologic immune responses can be initiated
locally within the lung, but only after a delay, during which lymphocytes
are recruited and organized at the site of infection. Although peripheral
lymphoid organs are not absolutely required for the initiation of immune
responses, these data do not contradict the idea that lymphoid tissues
facilitate immune responses and provide a significant benefit to the host,
particularly in response to highly virulent pathogens. Instead, the lung,
and perhaps other non-lymphoid organs, have the ability to organize local
immune responses; furthermore, they suggest that the immune response generated
in these local sites can be protective, yet functionally different, to
those initiated in conventional lymphoid organs. If so, then this argues
that vaccines that target immune responses to local tissues rather than
to conventional lymphoid organs may provide protection with reduced potential
for immune-mediated damage.
sustains hematopoiesis from foetal week 6 up to foetal week 38
extraembryonic yolk sac
(and intraembryonic splanchnopleura ?) sustains hematopoesis from foetal
week ? up to foetal week ?
Lymphocyte traffic between lymphoid tissues ensures that :
Ag-specific cells will be brought into contact with Ag
memory cells will be widely disseminated enabling a widespread response
"Lymphocyte trapping" concentrates recirculating lymphocytes in
regional lymph nodes where Ag has localized, thereby depleting Ag-reactive
lymphocytes from the circulating pool. This phenomenon is mediated by the
Ag-induced release of T cell cytokines and occurs within 24 hours of antigen
localization. Several days later activated blast cells are released into
the thoracic duct.